If you go by the images in the Quaker State ads, which you can find on eBay, the sign with the serif typeface is only used until 1931. The sans serif or block lettering sign with Certified - Guaranteed runs from 1932 to 1945. In 1946 they dropped the Certified - Guaranteed slogan. My two porcelain signs are stamped Baltimore Enamel N.Y. and are both quite heavy. There are a few later variation signs which are quite common and less desirable. Cheers, Don.
Last edited by coopersplace; Wed Jan 23 2019 06:07 PM.